This invention relates to a machine and a method for fitting and removing a tyre.
To perform the removal of a tyre from a rim and the subsequent fitting operation, the state of the art consists of tyre changer machines having a wheel-holder unit and at least one operating unit.
The wheel-holder unit is designed to support and rotate the wheel about an axis. The operating unit comprises the tools used in different operating steps which entail:                detaching the bead of the tyre from the annular end (that is, edge) of the rim (process also known as bead breaking);        removing the tyre from the rim, that is, removing the tyre from the housing defined by the space between the two annular edges of the rim;        fitting a new tyre on the rim, that is, positioning a new tyre in the housing.        
It should be noted that the expression “tyre changer machine” is commonly understood to refer to a machine which is able to both remove the tyre from the rim and then perform the fitting operation. It should also be noted that the term “bead” denotes the portion of the tyre running round the annular edge of the rim.
The wheel-holder unit comprises, for example, a locking system which fixes the wheel to a rotary supporting plate. Typically, the axis of rotation is vertical, even though it is preferable to adopt a solution with a horizontal axis if the machine is designed to operate on wheels of heavy vehicles.
The operating unit usually comprises at least one bead breaker tool (or bead breaker disc). During use, the rubber of the tyre bead overheats and the bead adheres to the rim due to a rubber vulcanization phenomena; it is therefore necessary to detach the bead from the edge of the rim before starting the removal step. During the bead breaking step, the wheel is rotated by the wheel-holder unit and the bead breaker tool exerts a pressure on the side wall of the tyre close to the bead causing detachment from the edge of the rim.
It should be noted that a tyre has two beads, corresponding to the two annular edges of the rim, so the tyre changer machines usually have a pair of bead breaker disks, each of which is designed to act on a corresponding bead of the tyre.
The rotary wheel-holder unit has a free end, to which the wheel is fixed, and an opposite end, connected to a drive unit. The positioning of the wheel on the wheel-holder unit makes it possible to define a lower side and a bead of the tyre, facing towards the end of the wheel-holder unit connected to the drive unit, and an upper side and a bead of the tyre, facing in the opposite direction to the lower side.
For this reason, the tools designed to act on the upper bead are referred to as upper tools, whilst the tools designed to act on the lower bead are referred to as lower tools.
In the tyre changer machines wherein the wheel-holder unit is configured with a vertical axis, the lower side and bead of the tyre face towards the supporting surface of the machine, that is to say, downwards, whilst the upper side and bead of the tyre face in the opposite direction relative to the lower side, that is to say, upwards.
The tyre changer machines are equipped with numerous tools, for bead breaking, removal and fitting of the tyre; typically, the tyre changer machines have tools designed to operate (in the bead breaking, removal and fitting steps) on the upper bead of the tyre and other, different, tools designed to operate (in the bead breaking, removal and fitting steps) on the lower bead of the tyre.
Each operating step requires the use of a specific tool or a specific combination of tools. In light of this, it should be noted that, typically, each tool is mounted on a respective supporting arm, actuated by a respective actuator and moved on a relative guide.
The presence of many movement apparatuses limits the vision of the operator in the proximity of the zone in which the machine operates on the wheel, hindering the freedom of movement of the operator.
This also translates into a significant increase in the dimensions of the tyre changer machines, which have a rather complex structure. The complexity of the machines increases the production and maintenance costs. Moreover, the increased complexity of these machines makes them more difficult to use by the operator to detriment of the reliability, thereby increasing the risks of error.
A partial solution to these problems is provided by patent document EP1479539, which has a machine having an operating head wherein a bead breaker disc is connected to a fitting/removal tool; this tyre changing tool is moved by a mechanism which allows it to change from one working position (that is, operational) to a non-interference position (that is, rest).
Patent document EP2125394 shows a machine having a rotary operating head with two tools; more specifically, the operating head has a bead breaker disc and a removal tool. The rotation of the head allows the selection of the tool. The same arm is connected to a fitting tool which, thanks to a hinge coupling, can be lowered or raised to adopt alternatively an operating position or a non-interference position.
Patent document EP1946946 shows a machine having a rotary operating head which supports three tools (a bead breaker tool, a removal tool and a fitting tool) arranged at 120°, in such a way as to be selectively and alternatively positionable in the operating position by rotating the operating head.
However, these tyre changer machines also have certain shortcomings, because they do not allow the tyre to be mounted in a particularly simple, reliable and comfortable fashion, with a particularly reduced number of actions by the tyre repair specialist.